On Wed, Mar 31, 2021 at 10:32 PM <guoren@xxxxxxxxxx> wrote: > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > - Using smp_cond_load_acquire in arch_spin_lock by Peter's > advice. > - Using __smp_acquire_fence in arch_spin_trylock > - Using smp_store_release in arch_spin_unlock > > All above are just coding conventions and won't affect the > function. > > TODO in smp_cond_load_acquire for architecture: > - current csky only has: > lr.w val, <p0> > sc.w <p0>. val2 > (Any other stores to p0 will let sc.w failed) > > - But smp_cond_load_acquire need: > lr.w val, <p0> > wfe > (Any stores to p0 will send the event to let wfe retired) > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > Link: https://lore.kernel.org/linux-riscv/CAAhSdy1JHLUFwu7RuCaQ+RUWRBks2KsDva7EpRt8--4ZfofSUQ@xxxxxxxxxxxxxx/T/#m13adac285b7f51f4f879a5d6b65753ecb1a7524e > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > --- > arch/csky/include/asm/spinlock.h | 11 ++++------- > 1 file changed, 4 insertions(+), 7 deletions(-) > > diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h > index 69f5aa249c5f..69677167977a 100644 > --- a/arch/csky/include/asm/spinlock.h > +++ b/arch/csky/include/asm/spinlock.h > @@ -26,10 +26,8 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) > : "r"(p), "r"(ticket_next) > : "cc"); > > - while (lockval.tickets.next != lockval.tickets.owner) > - lockval.tickets.owner = READ_ONCE(lock->tickets.owner); > - > - smp_mb(); > + smp_cond_load_acquire(&lock->tickets.owner, > + VAL == lockval.tickets.next); It's wrong, we should determine lockval before next read. Fixup: diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h index fe98ad8ece51..2be627ceb9df 100644 --- a/arch/csky/include/asm/spinlock.h +++ b/arch/csky/include/asm/spinlock.h @@ -27,7 +27,8 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) : "r"(p), "r"(ticket_next) : "cc"); - smp_cond_load_acquire(&lock->tickets.owner, + if (lockval.owner != lockval.tickets.next) + smp_cond_load_acquire(&lock->tickets.owner, VAL == lockval.tickets.next); > } > > static inline int arch_spin_trylock(arch_spinlock_t *lock) > @@ -55,15 +53,14 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock) > } while (!res); > > if (!contended) > - smp_mb(); > + __smp_acquire_fence(); > > return !contended; > } > > static inline void arch_spin_unlock(arch_spinlock_t *lock) > { > - smp_mb(); > - WRITE_ONCE(lock->tickets.owner, lock->tickets.owner + 1); > + smp_store_release(&lock->tickets.owner, lock->tickets.owner + 1); > } > > static inline int arch_spin_value_unlocked(arch_spinlock_t lock) > -- > 2.17.1 > -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
